Note: Some sharks, as the basking shark and the whale shark,
grow to an enormous size, the former becoming forty
feet or more, and the latter sixty feet or more, in
length. Most of them are harmless to man, but some are
exceedinglyvoracious. The man-eating sharks mostly
belong to the genera {Carcharhinus}, {Carcharodon}, and
related genera. They have several rows of large sharp
teeth with serrated edges, as the great white shark
({Carcharodon carcharias} or {Carcharodon Rondeleti})
of tropical seas, and the great blue shark
({Carcharhinus glaucus}) of all tropical and temperate
seas. The former sometimes becomes thirty-six feet
long, and is the most voracious and dangerous species
known. The rare man-eating shark of the United States
coast ({Charcarodon Atwoodi}) is thought by some to be
a variety, or the young, of {C. carcharias}. The dusky
shark ({Carcharhinus obscurus}), and the smaller blue
shark ({C. caudatus}), both common species on the coast
of the United States, are of moderate size and not
dangerous. They feed on shellfish and bottom fishes.
[1913 Webster]